Analytical Chemistry Methodologies Research Articles

Analysis of Metabolic Changes in Endogenous Metabolites and Diagnostic Biomarkers for Various Diseases Using Liquid Chromatography and Mass Spectrometry.

Analysis of endogenous metabolites in various diseases is useful for searching diagnostic biomarkers and elucidating the molecular mechanisms of pathophysiology. The author and collaborators have developed some LC/tandem mass spectrometry (LC/MS/MS) methods for metabolites and applied them to disease-related samples. First, we identified urinary conjugated cholesterol metabolites and serum N-palmitoyl-O-phosphocholine serine as useful biomarkers for Niemann-Pick disease type C (NPC). For the purpose of intraoperative diagnosis of glioma patients, we developed the LC/MS/MS analysis methods for 2-hydroxyglutaric acid or cystine and found that they could be good differential biomarkers. For renal cell carcinoma, we searched for various biomarkers for early diagnosis, malignancy evaluation and recurrence prediction by global metabolome analysis and targeted LC/MS/MS analysis. In pathological analysis, we developed a simultaneous LC/MS/MS analysis method for 13 steroid hormones and applied it to NPC cells, we found 6 types of reductions in NPC model cells. For non-alcoholic steatohepatitis (NASH), model mice were prepared with special diet and plasma bile acids were measured, and as a result, hydrophilic bile acids were significantly increased. In addition, we developed an LC/MS/MS method for 17 sterols and analyzed liver cholesterol metabolites and found a decrease in phytosterols and cholesterol synthetic markers and an increase in non-enzymatic oxidative sterols in the pre-onset stage of NASH. We will continue to challenge themselves to add value to clinical practice based on cutting-edge analytical chemistry methodology.

An Environmentally Friendly Compact Microfluidic Hydrodynamic Sequential Injection System Using Curcuma putii Maknoi & Jenjitt. Extract as a Natural Reagent for Colorimetric Determination of Total Iron in Water Samples.

The miniaturization of analytical systems and the utilization of nontoxic natural extract from plants play significant roles for green analytical chemistry methodology. In this work, the microfluidic hydrodynamic sequential injection (HSI) with the LED-phototransistor colorimetric detection system has been proposed to create an ecofriendly and low-cost miniaturized analytical system for online determination of iron in water samples using Curcuma putii Maknoi & Jenjitt. extracts as high stability and good selectivity of a natural reagent. The proposed method was designed for online solution mixing and colorimetric detection on a microfluidic platform. The Curcuma putii Maknoi & Jenjitt. extracts and standard/samples were sequentially aspirated to fill the channel before entering the built-in flow cell. The intensity of iron-Curcuma putii Maknoi & Jenjitt. extract complex was monitored under the optimum conditions of flow rate, sample volume, mixing zone length, and aspiration sequences, by altering the gain control of the colorimetric detector to achieve good sensitivity. The results demonstrated a good performance of the green analytical systems. A linear calibration graph in the range of 0.5-6.0 mg L-1 was obtained with a limit of detection at an adequate level of 0.11 mg L-1 for water samples with a sample throughput of 30 h-1. The precise and accurate measurement results were achieved with relative standard deviations in the range of 1.61-1.72%, and percent recoveries were found in the range of 90.6-113.4. The proposed method offers cost-effective, easy operation over an appropriate analysis time (2 min/injection) with good sensitivity and is environmentally friendly with low consumption of solutions and the use of high stability and good selectivity of nontoxic reagents. The achieved method was demonstrated to be a good choice for routine analysis.

Fuel effects on PAH formation, toxicity and regulated pollutants: Detailed comparison of biodiesel blends with propanol, butanol and pentanol

Blends of biodiesel and high-carbon alcohols have the potential to increase the rate of biofuel use in diesel engines, while reducing harmful and toxic compounds such as polycyclic aromatic hydrocarbons (PAHs). Since biodiesel and alcohols do not contain aromatic ingredients in their chemical structures, this study examined biodiesel blends with propanol, n-butanol, and 1-pentanol (5 %, 20 % and 35 % by vol.) and the effects of these aromatic-free fuels on regulated emissions, PAH formation and toxicity as compared to straight diesel fuel in a diesel engine operating at a constant speed and varying engine loads. PAH samples were meticulously processed and extensively analyzed using rigorous analytical chemistry methodology (gas chromatography–mass spectrometry (GC–MS)). Biodiesel and biodiesel-alcohol blends significantly reduced NOx emissions and the level of formation of PAHs and toxicity levels when compared to diesel fuel. Overall, adding 5 % alcohol to biodiesel decreased total PAH emissions. However, with the exception of 20 % propanol, adding 20 % and 35 % alcohol to biodiesel increased total PAH emissions as compared to neat biodiesel. In contrast, all blended fuels resulted in a decrease in the toxicity of PAH compounds (up to 70 %) and the percentage of higher-ring PAHs. Among higher alcohols, propanol blends stood out as reducing PAH formation as compared to n-butanol and pentanol blends. Overall, biodiesel-alcohol blends that emit less carcinogenic pollutants and primarily low-rings PAHs were found to be advantageous for reducing the likelihood of wetstacking in diesel engines under low load or cold operating conditions.

Metabolomics to understand placental biology: Where are we now?

Metabolomics, the application of analytical chemistry methodologies to survey the chemical composition of a biological system, is used to globally profile and compare metabolites in one or more groups of samples. Given that metabolites are the terminal end-products of cellular metabolic processes, or ‘phenotype’ of a cell, tissue, or organism, metabolomics is valuable to the study of the maternal-fetal interface as it has the potential to reveal nuanced complexities of a biological system as well as differences over time or between individuals. The placenta acts as the primary site of maternal-fetal exchange, the success of which is paramount to growth and development of offspring during pregnancy and beyond. Although the study of metabolomics has proven moderately useful for the screening, diagnosis, and understanding of the pathophysiology of pregnancy complications, the placental metabolome in the context of a healthy pregnancy remains poorly characterized and understood. Herein, we discuss the technical aspects of metabolomics and review the current literature describing the placental metabolome in human and animal models, in the context of health and disease. Finally, we highlight areas for future opportunities in the emerging field of placental metabolomics.

Probing Soil Electrochemistry: Electrochemical Characterization of Soil Via a Faradaic Approach

Soil is a vital component that holds together the Earth’s ecosystem. It plays an active role in biological events, hydrologic (water) cycle and behaves as a sink-source system for greenhouse agents (gases). More so, soil directly impacts growth of plants, crops and other vegetation. Commercially, soil quality determines the yield and type of farmland-wherein it is essential to have thorough information about soil parameters that is synchronized in terms of geological location (space) and period (time) due to variations associated with global change and land use. Implementation of soil sensors would be fundamentally beneficial to characterize the soil parameters in a local as well as global environmental-impact standpoint. Assessment of these parameters in soil samples in farm setting facilitates quantification and recording of its inherent physical and biochemical characteristics. Sufficient levels of soil nutrients is required for sustainable agricultural practices that typically exists as crop yield, pasture growth, etc. Currently, soil sampling and evaluation methods involve destructive and intrusive approaches to collect and then subsequently test the soil samples. Among this-Combustion method is one of the most widely sought after techniques to look at soil anatomy. Even with the upcoming research breakthroughs in non-destructive approaches like spectroscopy and tomography based models, there is a barrier in-terms of equipment complexity and availability as well as high costs and high logistical overhead. Therefore a sensing based ‘bottom-up’ approach is proposed in this study to probe soil matter and nutrient content. Soils are known to be dynamic systems under natural conditions and implementation of an integrated electrochemical and analytical chemistry methodology offers the added advantage of evaluating soil properties on-demand and in situ. Another main advantage of an electrochemical-analytical approach and the novelty of the proposed platform lies in the ability to profile soil at an interfacial level using a probe system and characterize the matrix in order to provide information in terms of various physico-chemical phenomena occurring at the electrode interface and correlate that to useful data that helps to understand soil fertility and bio-availability of nutrients for plants and other vegetation at the field level. There are a wide number of redox systems present in soil that exist in reduced state under ideal conditions (submerged). Soil is known to contain considerable amounts of these reducing substances as a function of organic matter content. In this work, faradaic measurements are utilized to determine threshold changes in soil electrochemical activity due to presence of various redox active substances present in the matrix. From preliminary data (Fig.1) and literature studies, there seems to be a high-correlation between electrochemical activity and presence of active substances that contribute to the soil-nutrient cycle which in turn differs in terms of various soil types. Therefore, probing these parameters could give further insight as to what in particular in the soil matrix contributes to the overall properties of soil type of a specific region. Results from this experimental question is used to track if confident deductions can be made with respect to constituency of soil matrix, assessing soil type, bulk density (BD), cation exchange capacity (CEC), electrical conductivity (EC), and electrochemical activity as a function of spatial and depth changes among other parameters. Figure 1

Paper-based sorptive phases for microextraction and sensing.

The simplification of the analytical procedures, including cost-effective materials and detectors, is a current research trend. In this context, paper has been identified as a useful material thanks to its low price and high availability in different compositions (office, filter, chromatographic). Its porosity, flexibility, and planar geometry permit the design of flow-through devices compatible with most instrumental techniques. This article provides a general overview of the potential of paper, as substrate, on the simplification of analytical chemistry methodologies. The design of paper-based sorptive phases is considered in-depth, and the different functionalization strategies are described. Considering our experience in sample preparation, special attention has been paid to the use of these phases under the classical microextraction-analysis workflow, which usually includes a chromatographic separation of the analytes before their determination. However, the interest of these materials extends beyond this field as they can be easily implemented into spectroscopic and electrochemical sensors. Finally, the direct analysis of paper substrates in mass spectrometry, in the so-called paper-spray technique is also discussed. This review is more focused on presenting ideas rather than the description of specific applications to draw a general picture of the potential of these materials.

Learning Something From Nothing: The Critical Importance of Rethinking Microbial Non-detects.

Accurate estimation of microbial concentrations is necessary to inform many important environmental science and public health decisions and regulations. Critically, widespread misconceptions about laboratory-reported microbial non-detects have led to their erroneous description and handling as “censored” values. This ultimately compromises their interpretation and undermines efforts to describe and model microbial concentrations accurately. Herein, these misconceptions are dispelled by (1) discussing the critical differences between discrete microbial observations and continuous data acquired using analytical chemistry methodologies and (2) demonstrating the bias introduced by statistical approaches tailored for chemistry data and misapplied to discrete microbial data. Notably, these approaches especially preclude the accurate representation of low concentrations and those estimated using microbial methods with low or variable analytical recovery, which can be expected to result in non-detects. Techniques that account for the probabilistic relationship between observed data and underlying microbial concentrations have been widely demonstrated, and their necessity for handling non-detects (in a way which is consistent with the handling of positive observations) is underscored herein. Habitual reporting of raw microbial observations and sample sizes is proposed to facilitate accurate estimation and analysis of microbial concentrations.

A simple flow injection spectrophotometric procedure for iron(III) determination using Phyllanthus emblica Linn. as a natural reagent

The use of natural reagents from plant extracts for chemical analysis is one approach in the development of green analytical chemistry methodology. In this work, a natural reagent extracted from Phyllanthus emblica Linn. has been applied for the determination of iron(III) using a simple flow injection spectrophotometric method. The method was based on the measurement of a dark-purple complex formed by the reaction between iron(III) and the extracted solution in an acetate buffer (pH 5.6) at 570 nm. Under the optimum conditions, a linear calibration graph in the range of 0.50–20.0 mg L−1 iron(III) was obtained with a correlation coefficient (r2) of 0.9996. The limit of detection and limit of quantification were 0.31 and 0.50 mg L−1, respectively. The relative standard deviation was less than 2.50%. The proposed method was successfully applied for quantitative analysis of iron(III) in pharmaceutical preparations and water samples with a sampling rate of 90 samples h−1. The results are in good agreement with those obtained by the official ICP-OES technique at the 95% confidence level. The presented method provides a simple, cost-effective and environmentally friendly approach which is suitable and useful for determining iron(III). Therefore, it can be considered as an alternative analytical technique in green chemistry.

Nitrate: An Environmental Endocrine Disruptor? A Review of Evidence and Research Needs.

Nitrate is heavily used as an agricultural fertilizer and is today a ubiquitous environmental pollutant. Environmental endocrine effects caused by nitrate have received increasing attention over the last 15 years. Nitrate is hypothesized to interfere with thyroid and steroid hormone homeostasis and developmental and reproductive end points. The current review focuses on aquatic ecotoxicology with emphasis on field and laboratory controlled in vitro and in vivo studies. Furthermore, nitrate is just one of several forms of nitrogen that is present in the environment and many of these are quickly interconvertible. Therefore, the focus is additionally confined to the oxidized nitrogen species (nitrate, nitrite and nitric oxide). We reviewed 26 environmental toxicology studies and our main findings are (1) nitrate has endocrine disrupting properties and hypotheses for mechanisms exist, which warrants for further investigations; (2) there are issues determining actual nitrate-speciation and abundance is not quantified in a number of studies, making links to speciation-specific effects difficult; and (3) more advanced analytical chemistry methodologies are needed both for exposure assessment and in the determination of endocrine biomarkers.

Human Toxicity Caused by Indole and Indazole Carboxylate Synthetic Cannabinoid Receptor Agonists: From Horizon Scanning to Notification.

The emergence of novel psychoactive substances (NPS), particularly synthetic cannabinoid receptor agonists (SCRA), has involved hundreds of potentially harmful chemicals in a highly dynamic international market challenging users', clinicians', and regulators' understanding of what circulating substances are causing harm. We describe a toxicovigilance system for NPS that predicted the UK emergence and identified the clinical toxicity caused by novel indole and indazole carboxylate SCRA. To assist early accurate identification, we synthesized 5 examples of commercially unavailable indole and indazole carboxylate SCRA (FUB-NPB-22, 5F-NPB-22, 5F-SDB-005, FUB-PB-22, NM-2201). We analyzed plasma and urine samples from 160 patients presenting to emergency departments with severe toxicity after suspected NPS use during 2015 to 2016 for these and other NPS using data-independent LC-MS/MS. We successfully synthesized 5 carboxylate SCRAs using established synthetic and analytical chemistry methodologies. We identified at least 1 SCRA in samples from 49 patients, including an indole or indazole carboxylate SCRA in 17 (35%), specifically 5F-PB-22 (14%), FUB PB-22 (6%), BB-22 (2%), 5F NPB-22 (20%), FUB NPB-22 (2%), and 5F-SDB-005 (4%). In these 17 patients, there was analytical evidence of other substances in 16. Clinical features included agitation and aggression (82%), reduced consciousness (76%), acidosis (47%), hallucinations and paranoid features (41%), tachycardia (35%), hypertension (29%), raised creatine kinase (24%), and seizures (12%). This toxicovigilance system predicted the emergence of misuse of indole and indazole carboxylate SCRA, documented associated clinical harms, and notified relevant agencies. Toxicity appears consistent with other SCRA, including mental state disturbances and reduced consciousness.

Surface mass spectrometry as a new approach for the characterisation of coffee

Coffee is the most widely traded tropical agricultural commodity in the world with global production for 2016 of over 151 million 60‐kg bags, according to the International Coffee Organization. Such popularity and its chemical complexity demand the development of analytical chemistry methodologies for the characterisation of different coffee compounds. This paper proposes the use of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) for this purpose. The main steps involving sample preparation and spectra acquisition are described alongside initial multivariate analysis results.

Green Analytical Methodology Using Indian Almond (Terminalia Catappa L.) Leaf Extract for Determination of Aluminum Ion in Waste Water from Ceramic Factories

The use of natural reagents from plant extracts for chemical analysis is one of the approaches in the development of low cost and environmentally friendly green analytical chemistry methodology. Here, crude extract from Indian Almond (Terminalia Catappa L.) leaves was used for colorimetric determination of aluminum by monitoring the absorbance of the Al(3+)-extract complex at 435 nm. Dry leaves and freeze-dried fresh leaf extract can be kept for extended use. A simple flow injection analysis (FIA) system was also employed for rapid analysis (approximately 180 injections/h). The linear working range up to 100 mg L(-1) was established with a detection limit (blank + 3SD) of 0.8 mg L(-1), a limit of quantitation (blank + 10SD) of 2.4 mg L(-1), and a relative standard deviation of 3-5%. This simple green analytical chemistry methodology was applied for the determination of Al(3+) in waste water samples from ceramic factories. The results agreed well with the results obtained from the ICP-OES technique.

Lab-on-a-chip fluorescence detection with image sensor and software-based image conditioning

The fluorometric detection in lab-on-a-chip devices for life-sciences is one of the main detection methods. Well know from “large-scale” analytical chemistry methodologies and instrumentation has been applied in lab-on-a-chip solutions. In most cases, optical instrumentation for fluorescence induction and detection is based on configuration and components borrowed from large laboratory instruments. As a result, optical instrumentation surrounding lab-on-a-chip is bulky, expensive and dedicated for operation only inside laboratory. In this paper a discussion on fluorescence detection in lab-on-a-chip is carried out. A novel image sensor – based detection instrumentation co-working with a “clever” software is described. Instrumentation is dedicated for operation in portable and low-cost devices for different life-science applications. Examples of applications of the novel method and instrumentation co-working with various lab-on-a-chips are presented on the base of author’s works.

MALDI- and ESI-MS of the HDL apolipoproteins; new isoforms of apoA-I, II

Apolipoproteins isolated from human high density lipoprotein were analyzed by matrix-assisted laser desorption (MALDI) and electrospray ionization mass spectrometry (ESI-MS). The long-term objective of this study is to identify and characterize new apolipoproteins and isoforms for clinical studies incorporating some of the latest advances in analytical chemistry methodology including mass spectrometry. The focus of this paper is on developing an understanding of the link between MALDI and ESI-MS data in the analysis of this complex mixture of proteins. Forty-nine peaks were observed in the MALDI spectrum and 11 species in the ESI-MS spectrum. The MALDI spectra consisted of peaks corresponding to known apoA and apoC molecular ion adducts and 11 species that could not be identified. The ESI-MS data provided excellent confirmation of MW values for the prominent ions in the spectrum. New isoforms of apoA-I and apoA-II were observed corresponding to truncation of C-terminal neutral amino acids. A new kind of isoform of apoA-II was discovered where the double strand is cleaved in vivo and the single strand is cysteinylated at the cleavage site. Confirmation was obtained by studying the change in the MALDI spectrum after performic acid oxidation. Charge-state distributions in the ESI-MS spectra were used to confirm the identity of this new isoform. The charge state distribution in ESI-MS was found to correlate with the number of basic residues in the apolipoprotein.

2,6‐cis‐Diphenylhexamethylcyclotetrasiloxane: Physico‐Chemical Properties and Analytical Methods

Abstract: The characterization of 2,6‐cis‐diphenylhexamethylcyclotetrasiloxane is presented in two parts. The first part‐physico‐chemical data—includes melting point, boiling point, vapor pressure and solubility data as well as spectroscopic data from infrared, ultraviolet, nuclear magnetic resonance and mass spectroscopic experiments. The second section describes analytical chemistry methodology for quality control: gas chromatographic separation and quantitation and nuclear magnetic resonance spectroscopy measurements.